Work platform



June 23, 1970 J. VAN DE VEGTE WORK PLATFORM '7 Sheet-Sheet l INVENTOR. JOHN VAN DE VEGTE 7%, 8m ffiw OK R vww :53..

DWN N N wmm mum wvw i 0mm ma NON Flled Sept 6, 1968 June 23, 1970 J. VAN DE VEGTE WORK PLATFORM 7 Sheets-Sheet 2 Filed Sept. 6, 1968 N rm INVENTOR. JOHN VAN DE VEGTE June 23, 1970 J. VAN DE VEGTE 3,516,257

WORK PLATFORM 4 7 Sheets-Sheet 3 Filed Sept. 6, 1968 2:: =1 7 f INVENTOR.

JOHN VAN DE VEGTE /|.J BY 250 250 I? uedhjax/ FIG. 7 7

June 23, 1970 J. VAN DE VEGTE 3,

WORK PLATFORM Filed Sept. 6, 1968 7 Sheets-Sheet 4 269d 2 g F g INVENTOR. JOHN VAN DE VEGTE June 23, 1970 J. VAN DE VEGTE 3,

WORK PLATFORM Filed Sept. 6, 1968 7 Sheets-Sheet 5 FIG.1O

INVEN'IOR. JOHN VAN DE VEGTE June 23, 1970 J. VAN DE VEGTE WORK PLATFORM 7 Sheets-Sheet 6 Filed Sept. 6. 1968 @Vm mmm mmm Vvm mvm Nmm @Vm vmm Vmm June 23, 1970 J. VAN DE VEGTE WORK PLATFORM 7 Sheets-Sheet 7 Filed Sept. 6, 1968 w El INVENTOR. JOHN VAN DE VEGTE United States Patent 3,516,257 WORK PLATFORM John Van de Vegte, Islington, Ontario, Canada, assignor to Boland Development Company Limited, Toronto, Ontario, Canada Filed Sept. 6, 1968, Ser. No. 757,980 Int. Cl. E21d 19/02 U.S. CI. 6145 12 Claims ABSTRACT OF THE DISCLOSURE A work platform supported between the walls of a mine tunnel and having a main frame having an upper platform to carry men and tools. An upper jack frame, powered by a screw motor, slides forwardly and rearwardly in the main frame below the platform. Four horizontal jacks of the upper jack frame project through horizontal slots in the sides of the main frame to grip the tunnel walls. A lower jack frame, below the upper jack frame, also has four horizontal jacks to grip the tunnel walls. The lower jack frame horizontal jacks project through generally vertical slots in the main frame walls, and the lower jack frame connects to the main frame by vertical jacks for relative vertical movement therebetween.

In another embodiment, the work platform has a main frame, and two large rotatable drums therein, each drum having two pairs of horizontal jacks to grip the tunnel walls. Rotation of the drums causes platform motion.

This invention relates to a work platform adapted to support itself between a pair of generally opposed spaced walls. Such a platform is particularly useful in mining applications.

In mines, tunnels are frequently encountered having irregular and often steep grades. It is frequently desired to position drilling (or other) machinery in such a tunnel e.g. to drill into the floor, Walls or roof of the tunnel, and to move the machinery along the tunnel as the work progresses. If the floor of the tunnel is highly irregular or steeply sloping, it is difficult to support machinery on such a floor and to move it along the tunnel.

Accordingly, the present invention provides a work platform which supports itself between the walls of such a tunnel, instead of on the tunnel floor. In a typical specific embodiment of the invention there is provided a work platform adapted to be supported between the walls of a mine tunnel and having a main frame having an upper platform to carry men and tools. An upper jack frame, powered by a screw motor, slides forwardly and rearwardly in the main frame below the platform. Four horizontal jacks of the upper jack frame project through horizontal slots in the sides of the main frame to grip the tunnel walls. A lower jack frame, below the upper jack frame, also has four horizontal jacks to grip the tunnel walls. The lower jack frame horizontal jacks project through generally vertical slots in the main frame walls, and the lower jack frame connects to the main frame by vertical jacks for relative vertical movement therebetween. Variations in this arrangement can of course be made if desired.

In a second embodiment the platform typically includes a pair of large rotatable drums mounted in a main frame, each drum having a pair of horizontal jacks thereon. By pressing the pads of one jack of each drum against the workspace walls and then rotating the drums, and repeating the procedure, the platform can be moved to any desired position.

Further objects and advantages of the invention will appear from the following disclosure, taken together with the accompanying drawings, in which:

FIG. 1 is a side view of an assembled work platform according to the invention;

FIG. 2 is a front view of the assembled work platform of FIG. 1 but without its front plate;

FIG. 3 is a side view of the main frame of the work platform of FIG. 1;

FIG. 4 is a front view of the main frame of FIG. 3 with the front plate removed;

FIG. 5 is a side view of the upper jack frame of the platform of FIG. 1;

FIG. 6 is a top view of the upper jack frame;

FIG. 7 is a front view of the upper jack frame;

FIG. 8 is a top view of the lower jack frame of the platform of FIG. 1;

FIG. 9 is a side view of the lower jack frame;

FIG. 9A shows a stabilizing bar to be connected between the lower jack frame and the main frame;

FIG. 10 is a sectional view of one of the bottom horizontal jacks of the platform of FIG. 1;

FIG. 11 is a sectional view of one of the top horizontal jacks of the work platform of FIG. 1;

FIG. 12 is a section along lines 1212 of FIG. 11;

FIG. 13 is an enlarged sectional view of the right hand side of the jack of FIG. 11 showing a fine adjustment mechanism therefor;

FIG. 14 is a view of the end of the frame tube of the jack of FIG. 11, showing slots at the end of the frame tube;

FIG. 15 is a diagrammatic side view showing further details of the fine adjustment mechanisms for the upper horizontal jacks, superimposed on a partial dotted outline of the work platform of FIG. 1;

FIG. 16 is an end view showing a frame welded to the frame tube of FIG. 14;

FIG. 17 is an end section showing a clearance strip and clearance bar used between the main frame and bottom jack frame of the platform of FIG. 1;

FIG. 18 is a side view of another embodiment of the invention;

FIG. 19 is a front elevational view of one of the two rotatable drums on the platform of FIG. 18; and

FIG. 20 is a more detailed view of the jacks at one end of a drum of the platform of FIG. 18.

Reference is first made to FIGS. 1 and 2, which illus trate a work platform 202 according to the invention. The work platform 202 includes a main frame 204, shown by itself in FIGS. 3 and 4. The main frame 204 as viewed from the side is generally in the form of a parallelogram having front and rear surfaces 206, 208 sloping at an angle (e.g. degrees) relative to the top and bottom surfaces. The main frame 204 includes a pair of side plates 210 braced by channels 212 and connected together by a front plate 214, a top plate 2.16, and bottom plates such as that shown at 218. For purposes of illustration, it is assumed in the embodiment described that the work platform is to be used in mines to drill holes in work faces for explosives, and accordingly, the main frame includes drill mounts 220 mounted on the top of the main frame. The drill mounts 220 support a drill boom not shown. (Top plate 216 extends forwardly only to the front of the drill mounts 220, so

that the drill boom can swing downwardly.) An operator platform 222 is mounted behind the drill mounts, on the top of the main frame. The operator platform is constituted by a simple deck structure formed from metal plates (with a hump in the middle for an actuating screw to be described). The operator platform 222, and an angle beam 223 at its rear, serve further to connect together the side plates 210.

The main frame further typically includes an air motor 224 supported on the boom plates 218 at the rear of the main frame. The air motor 224 is powered by air lines normally available in a mine and operates a pump 226 which pressurizes the oil from a tank 228 to drive the various hydraulic mechanisms on the work platform.

Finally, the side plates 210 of the main frame each include a pair of in line front and rear horizontal slots 230, 232 near the top of the main frame. These slots accommodate upper horizontal jacks of a top jack frame as will be described. The side plates of the main frame further include front and rear generally vertical slots 234, 236. These slots slant slightly forwardly and accommodate lower horizontal jacks of a bottom jack frame, as will also be described.

Reference is next made to FIGS. to 7 which illustrate an upper jack frame 238 for the work platform. The upper jack frame includes side plates 240 to which are connected (e.g. by welding) the frame tubes of a pair of upper horizontal jacks 242, 244. These jacks contain pressure pads 246a to 246d which press against the walls of the workspace when the jacks are extended. At its rear end the upper jack frame includes a counterweight support portion 248 having a pair of bottom bearing plates 250 (FIG. 6) projecting slightly inwardly from the side plates 240.

The upper jack frame 238 is mounted in the main frame 204 as follows. At its front, the upper jack frame 238 includes a pair of rollers 252 journalled on plates 254 welded to the side plates 240 of the upper jack frame. These rollers 252 bear against the underside 256 (FIG. 4) of the channels 212 at the sides of the main frame. At the rear of the upper jack frame, the hear ing plates 250 rides on rollers 258 (FIG. 3) similar to rollers 252 but journalled at the back of the main frame 204.

In addition, the outer frame tubes of the upper horizontal jacks 242, 244 extend through the slots 230, 232 at the sides of the main frame 204.

Relative motion between the upper jack frame 238 and the main frame 204 is achieved by a hydraulic motor 260 (FIG. 1) fastened in any desired manner to the main frame 204. The hydraulic motor 260 turns a long screw 261 which revolves inside a nut 262 (FIGS. 1, 5 and 6) fastened to the rear upper horizontal jack 244. In operation, assuming that the upper jack frame 238 is located in the position shown at FIG. 1 with respect to the main frame 204, with the upper horizontal jacks at the left hand sides of the slots 230, 232, then, when the screw is turned in the correct direction it will pull the upper jack frame 238 to the right and will move the upper horizontal jacks to the right in their slots, until the rear of the upper jack frame, including the counterweight support portion 248, is entirely retracted within the main frame.

The work platform 2 further includes a lower jack frame 263 shown in FIGS. 8 and 9. The lower jack frame includes a pair of side plates 264 to which are welded the outer frame tubes of front and rear lower horizontal jacks 266, 268. The lower horizontal jacks include pressure pads 269a to 269d adapted to be pressed against the walls of a workspace. In addition, the front surface of the jack 266 contains projecting brackets 270 to which are connected two front vertical jacks 272 (best shown in FIGS. 1 and 2). The front surface of the rear lower horizontal jack 268 contains a projecting support bracket 274. A stabilizing bar 276 (shown by itself in FIG. 9A) is pivotally connected at 278 to the support bracket 274 and is pivotally connected at 280 to the rear of the main frame. The stabilizing bar 276 extends downwardly from its connection 278 with the rear lower horizontal jack 268 to a further connection at 282 with a rear vertical jack 284. The vertical jacks 272, 284 are pivotally connected at 286, 288 respectively to the main frame 4.

The operation of the work platform as so far described is as follows. Assume that the platform is suspended between the walls of a workspace with the eight pressure pads of the four horizontal jacks all pushed firmly against the walls to hold the platform in position. Assume that the upper horizontal jacks are located at the front of the slots 230, 232 (i.e. at the right hand sides of these slots as shown in FIG. 1) and that the operator wishes to move the platform forwardly. The operator then retracts the pressure pads of the lower horizontal jacks 266, 268 inwardly, away from the workspace walls, leaving the machine supported only by the upper horizontal jacks 242, 244. He then actuates the hydraulic motor 260 to pull the main frame 204 to the right with respect to the upper jack frame 238, until the upper jacks 242, 244 are positioned at the left hand sides of the slots 230, 232 (as shown in FIG. 1). The upper jack frame 238 is held against movement at this time by the engagement of the upper horizontal jacks 242, 244 against the workspace walls. As the main frame 204 moves forward, it pulls the lower jack frame 263 with it because of the engagement of lower horizontal jacks 266, 268 in the vertical slots 234, 236 in the sides of the main frame (and because of the stabilizing bar connection).

After the main frame 204 has been pulled to the right as far as it will go, the pressure pads of the horizontal jacks 266, 268 of the lower jack frame are extended into firm engagement with the walls of the workspace. The pressure pads of the upper horizontal jacks 242, 244 are then retracted and the hydraulic motor 260 is again actuated to pull the upper jack frame 238 to the right relative to the main frame 204. The main frame 204 and lower jack frame 263 remain fixed at this time because of the engagement of the pressure pads of the lower horizontal jacks 266, 268 against the workspace walls. In this manner, the main frame and upper jack frame are moved alternately to achieve forward movement. The same procedure in reverse is used for reverse movement.

If upward movement is desired, the pressure pads of the lower horizontal jacks 266, 268 are fixed against the workspace walls, the pressure pads of the upper horizontal jacks 242, 244 are retracted, and the vertical jacks 272, 284 are extended to push the main frame 204 upwardly. As the main frame 204 rises, it carries the upper'jack frame 238 with it, because of the engagement of the plates 250 of the upper jack frame against the rollers 258 of the main frame, and because of the protrusion of the upper horizontal jacks 242, 244 through the slots 230, 232 in the side plates of the main frame 204. Because the typical application described is for a mine, in which the workspace will usually be tunnel sloping forwardly and upwardly, the vertical motion shown includes a 30 degree forward component for convenience.

After the vertical jacks are extended to the amount desired, the pressure pads of the upper horizontal jacks 242, 244 are extended firmly against the walls of the workspace, the pressure pads of the lower horizontal jacks 266, 268 are retracted away from the workspace walls, and the lower jack frame 263 is then raised by contracting the vertical jacks 272, 284. The vertical jacks 272, 284 are normally simple piston and cylinder hydraulic jacks, rather than screw jacks, and contain conventional lock valves (not shown) to hold them against suddent loss of pressure in the event of a failure else where in the hydraulic system.

Reference is next made to FIG. 10, which shows one of the bottom horizontal jacks 266. Both bottom horizontal jacks 266, 268 are identical.

The jack 242 includes an outer frame tube 290 welded to the side plates 264 of the lower jack frame 263. Floating within the frame tube 290- are a left hand inner jack tube 292 and a right hand outer jack tube 294. Both are held against rotation by a pin 296 extending through the frame tube 290 into a slot 298 in the outer jack tube 294 and a slot 300 in the inner jack tube 2.92.

The slots 298, 300 are each typically of length equal to 26 inches plus the diameter of the pin 296, thus providing for a maximum extension of each jack tube 292, 294 of 26 inches from the ends of the frame tube 290. Each jack tube includes at its end a ball tipped extension .302 on which is mounted one of the pressure pads 269a or 26912. Springs 304 encircle the ball tipped extensions 302 and press between the ends of the jack tubes and the pressure pads to prevent the pressure pads from flopping loosely.

The jack tubes 292, 294 are moved relative to each other by a hydraulic motor 306. The motor 306 is mounted on the outer or right hand jack tube 294 and is coupled by a coupling 308 to a screw 310'. As the screw 310 turns, it moves a nut 312 (which is splined at 314 on its outer surface to prevent rotation of the nut) towards the left in FIG. 10. The nut 312 pushes against the flange 316 of a sleeve 318 enclosing the screw 310 and pushes the sleeve 318 to the left. The flange 316 bears against a preloaded compression spring 320 (precompressed to a load of e.g. 20,000 pounds) and pushes this spring to the left. The left hand side of spring 320 bears against a flange 322 welded to the left hand jack tube 292 and thus pushes the left hand jack tube to the left.

Relative movement of the jack tubes continues until both pressure pads 269a, 26% of the jack 242 have been forced against the Workspace walls. Because the spring .320 is precompressed (even when the jack tubes 292, 294 are fully retracted) to a pressure of e.g. 20,000 lbs., the spring does not further compress until both pressure pads 269a, 26% are seated against the workspace Walls. Then, as the screw 310 continues to turn, the nut 312 moves to the left relative to the left hand jack tube 292 compressing the spring 320 further. By the time the right hand flange 325 of the nut 312 has moved so that it begins to contact a stop 326 connected to the right hand jack tube 294 (initially the nut flange and stop 326 are spaced apart by a distance d equal typically to 2 /2 or 3 inches), the left hand tip of tube 318 has depressed the actuator 328 of a pneumatic valve 330 to a substantial extent. Valve 330 is adjusted so that at this time it provides a pneumatic signal that the jack pads 269a, 26% are firmly in contact with the workspace walls. This pneumatic signal is applied in a pneumatic circuit, using conventional technology, to make withdrawing the pressure pads of the upper horizontal jacks from the workspace Walls impossible unless the pressure pads of both bottom horizontal jacks are in contact with the Walls at the desired force level. The pneumatic signal is also used to provide at all times to the operator an indication whether the pads are pressed against the Walls at the desired force.

The compression spring 320, and its extra compression by the distance d after the pressure pads have been pressed against the workspace walls, are provided for safety reasons, in case of slight crumbling of the workspace Walls. Without the spring 320, if the workspace walls compressed apart slightly or crumbled, all pressure of the pressure pads 269 against the walls would be lost and the platform would fall. With the spring, crumbling of the walls or their compression apart by distance equal nearly to distance d is possible, and the compression spring 320 will still force the pressure pads against the walls with a pressure equal to 20,000 lbs., which is normally suflicient to support the platform.

In use of the platform, it will often be essential to drill holes precisely parallel, e.g. to implant explosives in the walls or floor or roof of the workspace. Therefore, it is necessary to be able to rotate the main frame 204 of the work platform slightly in order to align the drilling machinery on the main frame as desired. For this purpose, the upper horizontal jacks 242, 244, which are identical, are provided with side positioning mechanisms now to be described. As shown in FIG. 11, the upper front hori- 6 zontal jack 242 includes a frame tube 332 welded to the side plates 240 (not shown in FIG. 11) of the upper jack frame. Located inside the frame tube 332 are a left hand inner jack tube 334 and a right hand outer jack tube 336.

Located within the inner jack tube 334 is a hydraulic motor 338, coupling 340, and bearing 342. This mechanism is connected to the frame tube 332 by a pin 344 extending through slots 346, 348 in the outer and inner jack tubes respectively. The slots limit extension of the jack tubes to 26 inches beyond the frame tube 332 and also prevents rotation of the jack tubes.

The motor 338 drives a screw 350 which moves a nut 352 similarly to the FIG. 10 arrangement. The nut 352 bears against a sleeve bearing in turn against a preloaded compression spring 354, to move the inner jack tube 334 and its pressure pad 246a against workspace wall 356.

The right han dor outher jack tube 336 has no sepa rate motive means. Instead, it is moved using the powered left hand or inner jack tube 334, which extends for this purpose nearly to the right hand end of the frame tube 332. At its right hand end the inner jack tube 334 contains a pneumatic actuator 358 (see also FIG. 12) having movable bolts 360. The bolts 360 are adapted to be pushed (by the actuator) into opposed ones of two series of diametrically opposed holes 362 in the outer or right hand jack tube 336.

In operation, to move the right hand or unpowered jack tube 336 from fully retracted to fully extended position, the inner or left hand powered tube 334 may be extended fully; the outer tube 336 may then be locked to the inner tube by the pneumatic jack bolts 360, and then the inner tube 334 may be retracted. This will extend the outer tube 336. This may also be done in smaller steps if desired.

When the outer and inner tubes 334, 336 are unlocked by withdrawing the bolts 360, some retaining means must be provided to retain the right hand or unpowered jack tube 336 in the position in which it has been left. This retaining means comprises a retaining bolt mechanism, not illustrated in FIG. 11 or 12 for clarity but shown in FIGS. 13 to 16. The retaining bolt mechanism includes a retaining bolt 364 long enough to pass through the opposed holes 362 in the outer jack tube and long enough to pass through slots 366 (FIG. 14) in the end of the frame tube 332. The retaining bolt 364 is held against a nut 368 turning on a thread 370 on the outer surface of frame tube 332 near the end of the frame tube. The nut 368 can be moved back and forth a distance equal approximately to the distance between two of the holes 362, and is turned by a chain 372 turning around a sprocket 373 welded to the nut. A similar chain 374 (FIG. 15) is provided for a similar nut for jack 266.

The retaining bolt 364 is held in position aginnst the face of nut 368 by a light cover 376 held by springs 377 to a frame 378 (see also FIG. 15) fastened to the frame tube 332. This allows some movement of the retaining bolt mechanism in case the bolt is pushed into holes 364 in the outer jack tube 336 while this tube is still moving outwardly. The cover 376 is equipped with lips 379 extending into the slots 366 of the frame tube 332 to prevent rotation of the cover. Guides 380 on the cover center the cover 376 on the nut 368 when the cover is pushed outwardly from the nut.

The retaining bolt 364 is moved into and out of engagement with the holes in the outer jack tube 336 by a spring return air cylinder 381 (FIG. 15). The connection between the air cylinder piston rod 382 and the bolt diagrammatically indicated at 384, has suflicient give to allow typically three inches lateral movement of the retaining bolt in the longitudinal direction of the frame tube. For safety, the bolt is biased into the holes in jack tube 336 by spring 386 and is Withdrawn by operating actuator 380. A similar bolt 388 and actuator 389 are provided for the rear upper horizontal jack 368.

The arrangement described permits positioning of the right hand jack tube in steps equal to the distance between the holes 362 (typically 1 /2 or 2% inches). Fine positioning of the right hand jack tube is achieved by the nut 368. The left hand jack tube may be moved continuously to any desired position because of the screw 350.

In operation, the right hand jack tube will be moved to within e.g. 2% inches of its desired position, using the powered left hand jack tube, and will then be stopped with the retaining bolt 364 being allowed to enter the nearest hole 362. Motion of the right hand jack tube 366 will then be resumed, with the retaining bolt 364 and bolt holder 376 moving therewith as allowed by the spring 377. When the right hand jack tube 336 has reached the desired position, the adjustment nut 368 is turned against the retaining bolt, after which the connection between the left hand and right jack tubes is removed. Since the adjustment nut 368 is operated under zero load, the chain 372 may be very light and may be turned by the operator.

It may be noted that during motion of the work platform from one point to another, the retaining bolts and adjustment mechanisms will almost never need to be operated. For example, to release the pressure pads of the upper horizontal jacks 242, 244 from the workspace walls, an operator will retract the left hand powered jack tubes (such as tube 334), then actuate the pneumatic jacks 358 inside the ends of these jack tubes so that the locking bolts 360 extend into the holes 362 in the right hand unpowered jack tubes when these present themselves. Further retraction of the left hand jack tubes then forces the right hand jack tubes to extend (the springs 377 allowing the retaining bolts and their holders to move with the right hand jack tubes), thus pushing the main frame 204 away from the workspace right hand wall. The left hand jack tubes are then extended again, causing the right hand jack tubes to retract away from the wall. All the pressure pads of the upper horizontal jacks are then away from the wall and the machine can be moved.

Usually only for lining up of the machine prior to drilling a new hole is adjustment necessary, and even then, if positioning parallel to the given line is suificient, the adjustment may be performed only on one of the two upper horizontal jacks.

To enable the above mentioned lining up of the main frame and operator platform thereon relative to a given reference line, it must be possible to rotate the main frame 204 in a horizontal plane when the pressure pads of the lower horizontal jacks 266, 268 are fixed against the workspace walls. Side motion of the lower jack frame 263 relative to the lower jacks 266, 268 is possible even when the bottom jacks are fixed against the walls because the bottom jack tubes can float in their frame tubes, but relative rotation requires clearance between the bottom jack frame 263 and the skirts or side plates 210 of the main frame 204.

Apart from the need for lining up the main frame, there should ideally be little or no clearance between the main frame 204 and the lower jack frame 238, since if there is clearance, the main frame will tend to take up some extreme position in the clearance range unless held by the top horizontal jacks. Therefore, the clearance needed to permit rotation of the main frame in a horizontal plane is provided only near the fully retracted position of the vertical jacks. This is the desirable position during drilling (since with the vertical jacks retracted the machine is more stable and the forces acting on it are lessened), so limiting rotational adjustment freedom to this condition is not a disadvantage.

Accordingly, variable clearance between the main frame 204 and the lower jack frame 263 is provided by four clearance strips 390 (see FIGS. 1, 2) connected to the side plates 210 of the main frame. The clearance strips cooperate with clearance bars 392 (FIGS. 8, 17) welded along the side plates 264 of the lower jack frame 263. The clearance strips have vertical sides and a sloped top 394 which provide clearance for the clearance bars 392 on the lower jack frame when the vertical jacks are fully retracted, but otherwise provide very little clearance.

While moving the work platform from one point to another, the operator will generally avoid the clearance range by stopping retraction of the vertical jacks when a beginning sag of the machine in some direction indicates that the clearance range is being entered. For lining up the machine after the desired position has been reached, the operator will place appropriate top jacks against the wall when sagging starts, and then fully retract the vertical jacks, after which he can then line up the main frame 204 using the top jacks. In order that side movement of the upper jack frame will cause corresponding side movement of the main frame 204, the frames 378 (FIGS. 13, 16) fastened to the upper jack frame tubes enclose fairly closely (but with a sliding fit) the main frame side plates 210 and channels 212. The frames 378 are located only at one side, not both sides, of the upper jack frame tubes.

Reference is next made to FIGS. 18 to 20, which show another embodiment of a work platform according to the invention. In this embodiment the platform includes a main frame 400 having frame channels 402 extending along each side thereof. The main frame 400 contains bearings 404 (FIG. 19) in which are mounted a pair of large drums 406, 408. These drums contain horizontal jacks 410, 412, 414 and 416. The drums 406, 408 can be rotated in unison by chains 418 engaging sprockets 420 encircling the drums, the chains being driven by a shaft 422 powered by a hydraulic motor 424. The jacks 410 and 416 are rotatable in the drums as the drums rotate, by means of bearings 426, 427. This rotational freedom is needed so that when e.g. the pads of jacks 410, 414 are fixed against the walls and the drums 406, 408 are rotated, the pads of jacks 410, 414 will not be disturbed.

The machine can be moved in any direction by alternately placing the bottom jacks 412, 416 and then the top jacks 410, 414 against the workspace walls and by rotating the drums in the directions needed to move the machine to a desired point. For example, with the bottom jacks against the wall in the position shown in FIG. 19, clockwise rotation of the drums will move the machine forward and downward. By then placing the top jacks against the walls and rotating the drums counterclockwise, further horizontal motion results. Because of hydraulic hose lines, not shown, the drums should not rotate 360 degrees. About degrees of rotation is adequate for motion in any desired direction.

As in the previous embodiment, the bottom jacks 412, 416 float sideways, and the top jacks 410, 414 are provided with fine adjustment mechanisms in order to line up the main frame relative to a reference line for drilling. In addition, as before, the main frame 400 must be rotatable in a horizontal plane while the bottom jacks are fixed against workspace walls. To permit this, the bottom jack tube bearing 427 (FIG. 19) are movable from side to side in slots 432 (FIG. 20) in the drums 406, 408. The jack tube bearings 427 are normally prevented from sliding in slots 432 by locking pins 434 which can be withdrawn by a pneumatic jack 436. When lining up is desired, the jack 436 retracts the locking pins, and the top horizontal jacks 410, 414 can be used to push the main platform to a desired orientation. Prior to moving the machine to another point, the bottom jacks are retracted and this allows self centering spring cartridges 438 on both sides of each bottom jack to recentre such jacks in their slots, after which the locking pins 434 can again lock the bottom jacks in position.

In all cases the operator controls for the platforms will be located on the main frame, usually on the operator platform. The control valves, oil and air lines, etc., may employ standard techniques and do not form part of the present invention, so they will not be described.

It will be apparent that various changes may be made in the machines described, particularly in the embodiment of FIGS. 1 to 17. For example, in that embodiment double horizontal jacks may be used for the horizontal jacks (as described in copending application Ser. No. 758,033 filed concurrently herewith by C. S. Boland). This increases Weight and cost but provides an alternative fine positioning means for the jacks. In addition, the positions of the upper and lower jack frames could be reversed, although this would limit the size of vertical steps available. In addition, the side plates and guide slots of the main frame could be eliminated and replaced by equivalent guiding and positioning means. A main feature of the FIGS. 1 to 17 embodiment is that by means of the three frames shown, forward and vertical movement of the machine having been made largely inde pendent of each other (except to the extent that a forward component has, in the platform illustrated, deliberately been introduced into the vertical movement to facilitate motion in a low, steep tunnel), and the operator has been placed above all other mechanism to reduce danger to him if the platform should fall.

What I claim as my invention is:

1. A work platform for use in a workspace having generally opposed spaced walls, said platform comprising:

(a) a main frame having an operator platform at the top thereof,

(b) first and second jack frames, each located below said operator platform and each having horizontal jack means having two pairs of opposed pressure members adapted to be selectively pressed against walls to support said work platform,

(c) first connecting means including vertical jack means connecting said first jack frame to said main frame for relative vertical movement therebetween, and for forward and rearward movement of said main frame to effect corresponding forward and rearward movement of said first jack frame, said first jack frame holding said main frame against substantial forward and rearward movement when the pressure members of said first jack frame are pressed against said walls,

(d) second connecting means connecting said second jack frame to said main frame for relative forward and rearward movement therebetween and fixing said second jack frame and said main frame against relative vertical movement therebetween,

(e) and motive means connecting said second jack frame and said main frame to effect forward or rearward movement of one relative to the other,

whereby the pressure members of said first jack frame may be pressed against said walls and those of said second jack frame may be retracted from said walls, said motive means then being operated to move said second jack frame forwardly or rearwardly relative to said main frame and first jack frame, said pressure members of said second jack frame then being pressed against said walls and those of said first jack frame retracted, said motive means then being operated to move said main frame and first jack frame forwardly or rearwardly relative to said second jack frame, thus to effect forward or rearward movement of said operator platform, vertical movement of said operator platform being achieved by said vertical jack means.

2. A work platform according to claim 1 wherein said first jack frame is a lower jack frame and said second jack frame is an upper jack frame located above said lower jack frame.

3. A work platform according to claim 2 wherein said main frame includes a pair of side skirts extending below said operator platform, said first and second jack frames being located between said side skirts, said side skirts including opposed generally horizontal slots therein through which the horizontal jack means of said upper jack frame project, and opposed generally vertical slots therebelow through which the horizontal jack means of said lower jack frame project.

4. A work platform according to claim 3 wherein said first connecting means includes a stabilizing bar pivotally connected to said main frame and pivotally connected to said lower jack frame, said vertical jack means including a vertical jack pivotally connected to said stabilizing bar.

5. A work platform according to claim 4 wherein the front and rear ends of said main frame, said vertical jack means, and said generally vertical slots, all slope slightly forwardly to facilitate movement of said Work platform in a low upwardly sloping tunnel.

6. A work platform according to claim 4 wherein said horizontal jack means of said lower jack frame are constituted by two jacks, namely a lower front horizontal jack and a lower rear horizontal jack, and said horizontal jack means of said upper jack frame are constituted by two jacks, namely an upper front horizontal jack and a lower rear horizontal jack, each horizontal jack including a frame tube connected to its associated jack frame and a pair of jack tubes, movable in opposite directions within said frame tube and protruding therefrom, and said pressure members being mounted at the tips of said jack tubes, said jack tubes of said lower horizontal jacks being mounted for limited floating side to side movement relative to their frame tubes.

7. A work platform according to claim 6 wherein each upper horizontal jack includes (i) screw means for extending and retracting one of the jack tubes thereof, said one jack tube extending longitudinally concentric with the other jack tube thereof,

(ii) locking means for locking said jack tubes together for movement of said one jack tube to move said other jack tube, and

(iii) retaining means located at the end of said frame tube from which said other jack tube projects, said retaining means including a retaining bolt adapted to be moved into a retaining position in which it engages said other jack tube to prevent retraction of said other jack tube, and means for moving said retaining bolt into and out of engagement with said other jack tube.

8. A work platform according to claim 7 wherein said retaining means includes a holder for said retaining bolt, and springs coupling said holder to said upper jack frame for limited outward movement of said holder and retaining bolt on the end of the frame tube on which said retaining means is mounted.

9. A work platform according to claim 8 including a nut mounted on the end of said frame tube on which said retaining means is mounted to adjust the effective location of said retaining means.

10. A work platform according to claim 3 wherein said first connecting means includes means providing a variable lateral clearance between the side skirts of said main frame and said lower jack frame, said clearance being a maximum when said vertical jack means are retracted so that said upper and lower jack frames are close together and being a minimum when said vertical jack means are extended to move said upper and lower jack frames apart.

11. A work platform for use in a Workspace having generally opposed spaced walls, said platform comprising:

(l) a main frame,

(2) a pair of enlarged drums mounted in said main frame for rotation therein,

(3) means for rotating said drums,

(4) each drum containing a pair of diammetrically opposed horizontal jacks extending therethrough, said jacks including pressure members adapted to press against the walls of said workspace,

(5) bearing means mounting said jacks for rotation,

about their axes, in said drums as said drums rotate,

(6) and means for selectively pressing the pads of selected ones of said jacks against said workspace walls, whereby the pressure members of one of said jacks in each drum may be pressed against said Walls, said drums may be rotated to move said work platform, the pressure members of the other two of said jacks may then be pressed against said walls, and said pressure pads of said first mentioned two jacks may then be retracted for further movement of said work platform.

12. A work platform according to claim 11 including means for selectively permitting side to side movement of one of said horizontal jacks in each of said drums,

12 to permit alignment of said work platform in said workspace.

References Cited UNITED STATES PATENTS 1,380,074 5/19'21 Myers 182-128 2,955,808 10/ 1960 Kandle 299-31 3,370,888 2/ 1968 Skendrovic 182128 X 3,379,264 4/1968 Cox 175--94 X FOREIGN PATENTS 1,306,821 9/1962 France.

826,971 1/1952 Germany. 69,272 5/ 1945 Norway.

DENNIS L. TAYLOR, Primary Examiner U.S. Cl. X.R. 6163 

